The Protein Biochemistry Group was involved in six major projects in FY 1992. Two projects, 1) the human decorin gene cloning, sequencing and chromosomal localization and 2) preliminary production and characterization of functional fragments of the integrin-binding bone sialoprotein (BSP) were brought to successful interim conclusions (Vetter et al., 1993 and Mintz et al., 1993 respectively). The discovery that human decorin has two exons-1 and therefore two independent promoters is continuing to be an area that we are exploring (Fisher, 1993). With our collaborators, the closely related biglycan gene has been eliminated as the genetic defect in the human disease Happle Syndrome (a chondrodysplasia punctata with streaky hyperkeratosis) (Traupe et al., 1993), although the gene maps very close to this disorder on the X chromosome. Our attempts to clone the dentin phosphophoryn, project 3, was as unsuccessful as that of several other laboratories around the world. Due to the importance of this molecule to the dental community, however, we continue to try new approaches. A new project was started (number 4) upon the arrival of Dr. John Stubbs from the graduate school of Rutgers University. This project involves the uncovering of the functions of the propeptides of the two small proteoglycans, decorin and biglycan. Project 5 is the cloning, sequencing and chromosomal localization of a cytoskeletal protein, drebrin. This gene product was originally thought to be a neurite-specific protein involved in dendrite formation. We think that this product may be involved in the formation of similar cellular extensions in the osteocyte, the arborizing lacunae. With Dr. Dan Deutsch, a visiting scientist from Hebrew University, Israel, we have conducted the final major project for 1992, the cloning, sequencing and chromosomal localization of the human enamel gene, tuftelin. At this time the gene is fully cloned and partially sequenced. The gene has been localized to chromosome 1, an interesting finding given that most of the cases of amelogenesis imperfecta (AI) are autosomal in inheritance.